JPH0847972A - Biaxially oriented polyamide film and production thereof - Google Patents

Abstract

PURPOSE:To provide a biaxially oriented polyamide film excellent in bending pinhole resistance, dimensional stability and longitudinal tearing linearity. CONSTITUTION:A biaxially oriented polyamide film is based on a mixture of nylon 6 (N6) and aliphatic polyamide resin (PA) other than N6 in a wt. ratio of (75-99/(25-1) and characterized by that the difference between the surface tension (dyne/cm) of N6 and that of PA satisfies formula 3.0<=gammaA-gammaB<=1 (wherein gammaA is the surface tension of N6 and gammaB is the surface tension of PA) and has longitudinal tearing linearily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a mixture of nylon 6 (N6) and another aliphatic polyamide resin (PA) as a main raw material and has excellent tear straightness in the longitudinal direction of the film and excellent mechanical properties. TECHNICAL FIELD The present invention relates to a biaxially oriented polyamide film having a high mechanical strength, heat resistance, oil resistance, solvent resistance, and dimensional stability, which is suitable as a packaging material for foods, pharmaceuticals, sundries and the like.

[0002]

2. Description of the Related Art Various plastic film packaging bags are often used for packaging foods, pharmaceuticals, sundries, etc. Two layers or three layers of biaxially stretched plastic film and heat-sealable non-oriented film are used. Packaging bags laminated with more than one layer are widely used. Especially in the fields where durability, heat resistance, oil resistance, solvent resistance, mechanical strength, etc. are required, a flat simultaneous biaxial stretching method as a biaxially oriented film,
A high-strength biaxially oriented polyamide film manufactured by a flat successive biaxial stretching method, a tubular method or the like is used.

The packaging bag using these biaxially oriented polyamide films has a problem that the tearing and unsealing property is poor, and a notch may be provided as a device for improving the unsealing property. However, when tearing from the notch, a phenomenon often occurs in which the packaging bag is not easily torn in the longitudinal or lateral direction or linearly. In such a case, the opening is performed along the distorted line, and excessive force is applied to try to tear it forcibly, resulting in the contents being scattered and wasted, as well as the contents. If the object is liquid, an accident such as soiling of clothes may occur. In order to solve such a problem, a method of laminating a biaxially oriented polyamide film and a heat-sealable non-oriented film to weaken the sealing strength to form a bag, and tearing the bag from the seal portion to open the bag is adopted. However, if the contents cannot be opened successfully, or if they are handled during transportation before opening, the contents may scatter from the seal part.
Improvement is required.

As an easily openable material which is excellent in straightness when the film is torn, there is a material obtained by laminating a uniaxially oriented polyolefin film as an intermediate layer. For example,
There is a three-layer laminate film of biaxially oriented polyamide film / uniaxially oriented polyolefin film / non-oriented polyolefin film. However, in this case, although the tear straightness of the uniaxially oriented film in the stretching direction is improved, a multilayer structure in which a new intermediate layer is provided only for improving the straight tearability of the film causes a problem such as an increase in cost. It remained and had limited uses.

As an easily tearable film, N6 contains 15 to 60
A biaxially stretched film made of a mixed polyamide mixed with wt% of MXD6 (polymethaxylylene adipamide) and a laminate film thereof have been proposed in JP-A-5-220837 and JP-A-5-200958. However, such a film mixed with MXD6 has a problem that pinhole resistance is high, and in particular, pinholes are frequently generated due to bending fatigue.

[0006]

SUMMARY OF THE INVENTION The present invention is intended to solve the above problems and has excellent durability, heat resistance, oil resistance, solvent resistance, mechanical strength, food, etc. To provide a biaxially oriented polyamide film suitable as an easy-open packaging material that has practical heat-resistant dimensional stability in a dry heat or wet heat environment and has tearing linearity in the longitudinal direction of the film. To do.

[0007]

The present inventors have arrived at the present invention as a result of extensive studies to solve such problems.

That is, the gist of the present invention is as follows. A biaxially oriented polyamide film containing a mixture of N6 and PA in a weight ratio of 75 to 99/25 to 1 as a main raw material.
A biaxially oriented polyamide film having linear tearability in the longitudinal direction of the film, characterized in that the difference in the surface tension (dyne / cm 2) of PA and PA satisfies the formula (1). 3.0 ≦ γ _A −γ _B ≦ 15.0 (1) where γ _A represents the surface tension of N6 and γ _B represents the surface tension of PA.

The N6 used in the present invention includes not only N6 homopolymers but also copolymers containing 90 mol% or more of N6.

As the PA used in the present invention,
For example, those containing 90 mol% or more of nylon 7, nylon 8, nylon 9, nylon 10, nylon 11, nylon 12, nylon 69, nylon 610, nylon 612, etc., may be used alone or blended, or , N6 copolymers can be used. Most preferably, the copolymerization molar ratio of N6 and other nylon polymers constituting the copolymer is 20-80 / 80-20.

Of these, nylon is particularly preferable.
11, nylon 12, nylon 69, nylon 610, nylon
612, nylon 6/11 (copolymer of nylon 6 and nylon 11) and nylon 6/12 (copolymer of nylon 6 and nylon 12).

In the film of the present invention, it is necessary to use a mixture of N6 and PA in a weight ratio of 75 to 99/25 to 1 as a main raw material. If the proportion of PA is less than 1% by weight, straightness of tearing is not exhibited, and if it exceeds 25% by weight, mechanical properties such as flex pinhole resistance of the film are deteriorated, which is not desirable. P
The preferable range of the ratio of A is 15 to 2% by weight, and more preferably 10 to 3% by weight.

Polyamides other than N6 and PA, for example, aliphatic polyamides such as nylon 46 and nylon 66, alicyclic polyamides, aromatic ring-containing polyamides, and polymers other than polyamides, for example, polyamides, such as N6 and PA 66, can be used as long as the effects of the present invention are not impaired. , Polyethylene, polypropylene, polystyrene, etc. may be contained.

Further, within a range that does not impair the effects of the present invention,
It may contain various additives for polyamide. Such additives include silica, inorganic lubricants such as calcium carbonate and organic lubricants, antioxidants, ultraviolet absorbers,
Examples include deterioration preventing agents, antiblocking agents, antistatic agents, fillers and pigments.

The surface tension of a polymer is used as an index of the compatibility of two or more polymers. In the present invention, the surface tension difference (Δγ) between N6 and PA needs to be 3.0 to 15.0, preferably 4.0 to 12.0, and more preferably 5.0 to 9.0.

The surface tension (γ) used in the present invention is a calculated value based only on the chemical structure of the substance obtained by the equation 1.
[Where ΔE _i is the contribution of each atom to the molar cohesive energy due to the interaction of each atom (J / mol), and ΔV _i is the van d
er Waals Volume increment (Å ³ ), A indicates the number of atoms in the repeating unit. ]

[0017]

[Equation 1]

That is, since the surface tension of N6 is 45.2, the surface tension of PA when mixed with N6 is 30.2 to 42.2.
The polymer must be within the range. In this case, N6 and PA have a suitable compatibility with each other, and PA is N
Dispersed in No. 6 in an appropriate size, and tear straightness is exhibited.
If the difference in surface tension is less than 3.0, the compatibility of both polymers is too good to achieve straightness of tearing, and if it exceeds 15.0, the balance between melt tension and stress relaxation of molecular chains is improper and the thickness of the unstretched sheet formed is small. Unevenness increases and stable tear straightness cannot be obtained.

The melting point of PA in the present invention is preferably lower than that of N6. If the melting point of PA is higher than N6, a uniform unstretched sheet may not be obtained.

In the present invention, the melt viscosity of PA is N6.
It is desirable that the range is 0.1 to 4.0 times, preferably 0.2 to 2.0 times. If the melt viscosity ratio (hereinafter, referred to as PR) is less than 0.1, the dispersed particle size of PA becomes too small and the tear straightness of the film deteriorates, and the PR of 4.
If it exceeds 0, the dispersed particle size becomes too large, and the linear tearability of the film deteriorates, which is not preferable.

In the present invention, the glass transition temperature of PA is higher than the crystallization temperature of N6 (166 ° C. for N6 alone).
It is desirable that the temperature is 20 ° C. or higher, and more preferably 30 ° C. or lower.

The reason for this is that the glass transition temperature of PA is N6.
If the temperature is higher than the crystallization temperature of, the PA is in a glass state at the time when N6 starts to crystallize in the film manufacturing process, and it becomes difficult to control the shape of the dispersed particles of PA in the stretching process, resulting in a stable straight tearing. This is because the sex cannot be obtained.

In the unstretched sheet, the present inventors have
As a method of observing the dispersion state of PA in 6, the transmitted scattered light illuminance anisotropic ratio (hereinafter,
IAR) was used. IAR is the ratio of the illuminance of transmitted scattered light in the film longitudinal direction and the film width direction.
The closer to 0 is, the longer axis direction of the PA dispersed particles is more strongly oriented in the film longitudinal direction, and the closer the IAR is to 1, the closer the PA dispersed particles become spherical. By using this IAR, the shape and dispersed state of PA dispersed particles in an unstretched sheet can be observed, which is useful in considering the relationship with the tear straightness of the biaxially stretched film of the present invention. .

In the present invention, an unstretched sheet having an IAR value of 0.1 to 0.8 is stretched at a stretching ratio of 2.5 times or more in the stretching step so as to have tear straightness in the longitudinal direction of the film. A biaxially oriented polyamide film can be efficiently obtained.

It is difficult to stably produce an unstretched sheet having an IAR of less than 0.1 and extremely oriented in the longitudinal direction of the film, and when the IAR exceeds 0.8, stable stretching of the stretched film in the longitudinal direction is achieved. It is not preferable because tear straightness cannot be obtained.

As the production conditions of the film of the present invention, the temperature of the molten polymer and the time until the molten polymer extruded in a sheet form from the die contacts the cooling drum and is rapidly cooled are controlled within a certain time. It is important to.

The reason for this is that by preventing the recovery of the deformation of the dispersed particles of PA in the longitudinal direction of the film until the molten polymer comes into contact with the cooling drum, the dispersed particles of PA have their major axis in the longitudinal direction of the film. This is to maintain the shape as it has and to obtain stable tear straightness in the longitudinal direction of the film. Generally, the lower the temperature of the molten polymer and the shorter the time until the molten polymer comes into contact with the cooling drum, the longer the shape of the dispersed particles of PA becomes in the film longitudinal direction.

That is, the weight ratio of N6 and PA is 75 to 99 /
The mixture of 25 to 1 was extruded from the lip gap of the die into a sheet, and the shear rate of the molten polymer was 100 to 40.
Assuming that ⁰ sec ⁻¹ , the relationship between the temperature (PT) of the molten polymer extruded from the lip gap of the die and the time (t) until the molten polymer reaches the cooling drum is described in (1) to
The unstretched sheet obtained by controlling as in (5) was adjusted to have a moisture content of 1 to 6% by weight, and then at a temperature of 150 to 220 ° C., the stretching ratio was 2.5 times or more in each of the longitudinal and transverse directions. Stretching is preferred.

(1) When PT is in the range of 240 ≦ PT <250 ° C., t ≦ 1.2 seconds. (2) t ≤ 0.9 when PT is in the range of 250 ≤ PT <260 ℃
Seconds. (3) t ≤ 0.6 when PT is in the range of 260 ≤ PT <270 ℃
Seconds. (4) t ≦ 0.3 when PT is in the range of 270 ≦ PT <280 ℃
Seconds. (5) t ≦ 0.1 when PT is in the range of 280 ≦ PT <290 ℃
Seconds.

In general, the greater the draft ratio (ratio of the lip gap of the die to the thickness of the unstretched sheet: DR) or the greater the stretching ratio in the longitudinal direction, the more P
The shape of the dispersed particles A is elongated in the longitudinal direction of the film.

As the method for producing the biaxially oriented polyamide film of the present invention, a tube line flation method, a tenter simultaneous biaxial stretching method, and a sequential biaxial stretching method using a roll and a tenter can be used. The tenter simultaneous biaxial stretching method will be described.

A mixture having a weight ratio of N6 and PA of 75 to 99/25 to 1 is put into an extruder, heated and melted, and then extruded in a sheet form from a T die and discharged. Next, the sheet discharged from the T die and in a softened state is wound around a cooling drum to be cooled. The obtained unstretched sheet is adjusted to have a water content of 1 to 6% by weight, and then simultaneously biaxially stretched at a temperature of 150 to 220 ° C. with a stretching ratio of 2.5 times or more in each of the longitudinal and transverse directions. Subsequently, the biaxial orientation is fixed by heat treatment in a temperature range below the melting point of N6 and above the melting point minus 40 ° C.

The biaxially oriented film obtained by stretching and heat treatment is, if necessary, subjected to physicochemical surface treatment such as corona discharge treatment or coating on one or both sides in order to impart easy adhesion. It

Since the film of the present invention has excellent toughness, practical strength, heat-resistant dimensional stability, and tear straightness in the longitudinal direction of the film, it is suitable as an easily openable packaging material for foods, pharmaceuticals, sundries and the like. is there.

When the film of the present invention is used for a packaging bag, it is usually polypropylene, polyethylene, ethylene-vinyl acetate copolymer, polyester or the like in order to impart heat sealability or gas barrier property. It is used by being laminated with other plastic film, paper, metal foil such as aluminum. In this case, the film of the present invention is used for at least one layer, and the number of laminated layers is not particularly limited as long as the laminated film has a linear tearing property.

By making such a laminated film into bags so that the longitudinal direction of the film of the present invention is the tearing direction, an easily openable packaging bag is obtained. And since this packaging bag has excellent tear straightness, soup, jam,
Foods such as retort pouches, pharmaceuticals, daily necessities,
It is useful as a packaging bag for toiletries.

[0037]

In the present invention, since the interaction between the PA dispersed in an island shape and the interface of N6 forming the matrix is small, the stress at the time of tearing concentrates in this portion, and thus the rectilinear tearing property appears. Be done.

[0038]

EXAMPLES Next, the present invention will be specifically described with reference to examples. The raw materials and measuring methods used in the evaluation of the examples and comparative examples are as follows.

(1) Raw material N6; nylon 6 manufactured by Unitika, trade name: A1030BRF nylon 610 (N610); (aliphatic polyamide from hexamethylene diamine and sebacic acid) Showa Denko, trade name: Technyl D316 nylon 69 (N69); in an autoclave (volume 68.3 l)
25.5 l of water and 945 g of azelaic acid were added and stirred. Meanwhile, add 10.5 l of 75% hexamethylenediamine aqueous solution.
After adjusting to 80 ° C. and pH 7.60 to 7.63, the mixture was charged into the autoclave, reacted in a closed system under a nitrogen atmosphere at 250 ° C. for 6 hours, and then depressurized to obtain 13.5 kg of a polymer of nylon 69.

Nylon 6/11 (N6 / 11); ε-caprolactam 5.0 kg, 11-aminoundecanoic acid 8. in autoclave.
Add 9 kg and 1.0 kg of water and slowly raise the temperature to 260 ° C.
After 2 hours, the internal pressure was adjusted to 4 kg / cm ² . After reacting at 260 ℃ for 2 hours, gradually remove the generated steam, release the pressure to return to normal pressure, and further reduce the pressure to react for 1.5 hours,
A polymer of nylon 6/11 was obtained.

Nylon 6/12 (N6 / 12); ε-caprolactam 5.0 kg, 12-aminododecanoic acid 9.5 in an autoclave
Add 1.0 kg of water and 1.0 kg of water and slowly raise the temperature to 260 ° C.
After a period of time, the internal pressure was adjusted to 4 kg / cm ² . After reacting at 260 ° C. for 2 hours, the generated steam was gradually removed, the pressure was released to return to normal pressure, and the pressure was further reduced to react for 1.5 hours to obtain a polymer of nylon 6/12.

Nylon 612 (N612); equimolar amounts of hexamethylenediamine, dodecanedioic acid and water were put into an autoclave, heated at 150 ° C. under a slight pressure to a salt concentration of about 80%, and concentrated. Heated to 15-20 atm. Then, heat it up to 250 ℃ at 15 to 20 atm to gradually remove the generated steam, release the pressure and return to normal pressure, raise the internal temperature to 270 to 280 ℃ and reduce the pressure. Got

Nylon 11 (N11); (Aliphatic polyamide by polycondensation of 11-aminoundecanoic acid) Toray Co., trade name: Rilsan BMNO Nylon 12 (N12); (obtained by ring-opening polymerization of ω-laurolactam Aliphatic polyamide) EMS Chemie, trade name: Grillamide L16 nylon 66 (N66); (Aliphatic polyamide from hexamethylenediamine and adipic acid) ICI, trade name: Maranyl A226 AN-1; Acid 2.68 kg, 4,
3.89 kg of 4 ^, -diamino-3,3 ^, -dimethyldicyclohexylenemethane, 3.76 kg of aminododecanoic acid and 5 kg of water were added, and the mixture was polymerized at 260 ° C. and an internal pressure of 18 kg / cm ² for 2 hours. The pressure was released and the product was discharged to obtain a transparent copolymer nylon (denoted as AN-1).

(2) Measurement method, etc. (a) Glass transition temperature The thermal characteristics of each sample were analyzed by DSC7 manufactured by Perkin Elmer and determined from changes in the baseline during temperature increase and decrease.
The glass transition temperatures of the polymers used in Examples and Comparative Examples are shown in Table 1.

(B) Surface tension: Mitsubishi Research Institute software "Polymer material design support system EXPOD" was installed on Sony workstation NET WORK STATION NWS-1.
It was run on 860 and NEW-OS R3.3 and calculated by the above equation. Table 1 shows the surface tensions of the polymers used in Examples and Comparative Examples.

(C) Melt viscosity: The melt viscosity of the resin dried under vacuum at 100 ° C. for 10 hours was measured by a flow tester (Shimadzu CFT-500) equipped with a nozzle having a diameter of 0.5 mm and a length of 2.0 mm.
Was measured at four points under conditions of a temperature of 280 ° C. and a preheating time of 180 seconds while changing the load. The apparent melt viscosity at a shear rate of 1000 sec ⁻¹ was read from the obtained shear rate-melt viscosity curve. The unit is N · sec · m ⁻² . Table 1 shows the melt viscosities of the polymers used in Examples and Comparative Examples.

[0047]

[Table 1]

(D) Transmitted scattered light illuminance anisotropic ratio (IAR);
After melt extrusion, the IAR of the cooled unstretched sheet was measured as follows. An unstretched sheet is placed on the stage of an optical microscope with a lens barrel and the like removed in a dark room, and the film transmitted scattered light illuminance ( _IM ) of the light source light in the azimuth direction of the film observed by the unstretched sheet is measured at a distance from the light source. 40m
Digital illuminometer DX- installed at m and elevation angle of 30 °
It measures in the range 1 using 100 (made by Kagaku Kyoeisha). Next, the stage was rotated by 90 °, and the film transmitted scattered light illuminance ( _IT ) of the light source light in the direction of the film width direction observed by the unstretched sheet was measured in the same manner, and IAR was obtained from the following equation. The assay system for the IAR = I _M / I _T scattered light intensity anisotropic ratio shown in FIG.

(E) Tear straightness in the longitudinal direction: A strip-shaped film piece 205 mm in the longitudinal direction and 40 mm in the width direction was cut out from the biaxially oriented film, and the length was measured at the center of one short side of the film piece. Make 10 samples with a 5 mm cut (Fig. 2). Next, tear by hand in the direction of the long side from the notch, and as shown in Fig. 3 (a), the number of samples that reached the short side where the tear propagation end faces the side where the notch was made is the evaluation value of the tear straightness in the longitudinal direction. (Evaluation value: 0 to 10).
The evaluation was carried out for each of the left end portion, the center portion and the right end portion of the film wound after stretching.

(F) Haze: As an index of transparency, the haze of a film having a thickness of 15 μm is ASTM D 1003−
The measurement was performed according to 61. In the evaluation of the film, haze ≦ 10% was evaluated as ◯, 10% <haze ≦ 20% was evaluated as Δ, and haze> 20% was evaluated as x.

(G) Flexing pinhole resistance; 20 ° C, 65% R
Attach a rectangular film of 20.3mm x 27.9mm, which was conditioned under the condition of H, to a Gelbo Flex Tester (manufactured by Rigaku Kogaku Co., Ltd.), rotate 440 ° while going straight for 8.9mm, and then go straight for 6.4mm. In the reverse stroke, the number of movements to return to the original position was counted as 1 and the bending test was performed 10000 times. With respect to the film after the bending test, a coloring liquid (Ageless seal check manufactured by Mitsubishi Gas Chemical Co., Inc.) was applied to one surface of the film, and the number of permeation of the liquid to the other surface was measured as the number of pinholes (measurement area was 497 mm ² ).

(H) Heat shrinkage rate: A strip sample having a marked line in each of the longitudinal direction (MD) and the width direction (TD) of the film was cut out and treated in an oven at 160 ° C. for 5 minutes, and after treatment. The dimension between the marked lines was measured at 20 ° C and 65% RH equilibrium, and expressed as a percentage of the amount of shrinkage due to the treatment with respect to the dimension before treatment. In addition, the compounding composition (% by weight) of the compositions of Examples 1 to 17 and Comparative Examples 1 to 7 is shown in Table 2.

[0053]

[Table 2]

(I) Resin temperature (P
T); using an infrared radiation thermometer 505S manufactured by Minolta
EMISSIVITY (emissivity) 0.99 about 1m in the direction perpendicular to the seat
Measured from the distance.

(J) Time (t) until the molten polymer extruded in a sheet form from the T die comes into contact with the cooling drum and is rapidly cooled; calculated from the following equation of constant acceleration linear motion. V ² −V ₀ = 2aS, V = V ₀ + at V: Speed after t seconds (rotational speed of cooling drum) V ₀ : Speed of molten polymer immediately after being extruded from the T die into a sheet shape (rotation of cooling drum) Velocity / DR) a: Acceleration S: Distance from the T-die to the cooling drum for the molten sheet t: Time for the molten sheet to reach the cooling drum from the T-die (k) Shear of the polymer passing through the lip of the T-die Speed (D _W ); D _W = (6Q) / (Wd ² ) Q: Discharge amount W: T die width d: T die lip gap.

Example 1 A composition was prepared by mixing N6 and N610 in a weight ratio of 95/5. (Γ _A −γ _B = 5.6, PR = 1.1) This composition was melt extruded at a resin temperature of 280 ° C. using a 100 mm φ extruder equipped with a coat hanger type T die, and the temperature was adjusted to 20 ° C. Then, it was closely cooled to a cooling drum to obtain an unstretched sheet having a thickness of about 150 μm. At this time, the interval between the slits of the T-die is about 1.3 mm, V = 21 m / min, S = 0.10 m
, D _W = 141 sec ⁻¹ , t = 0.51 sec, DR = 8.7,
IAR = 0.6. Obtain the unstretched sheet at 50 ° C
It is sent to a hot water tank adjusted to 2 minutes and subjected to a water immersion treatment for 2 minutes to a moisture content of 4.9%.
It was held in a clip of an axial stretching machine and stretched 3.0 times in the longitudinal direction and 3.3 times in the transverse direction under the condition of 175 ° C, and then subjected to a heat treatment for 4 seconds at 210 ° C with a transverse relaxation treatment of 5%, The mixture was gradually cooled to room temperature to obtain a biaxially oriented film having a thickness of 15 μm.
Tear linearity and bending pinhole resistance of the obtained biaxially oriented film were measured, and the results are shown in Table 3. As shown in Table 3, the film showed bending pinhole resistance and transparency equivalent to those of the N6 biaxially oriented film, and had excellent heat resistance dimensional stability and tear straightness in the longitudinal direction of the film.

Examples 2 to 3 Biaxially oriented films were obtained in the same manner as in Example 1 except that the mixing weight ratio of N 610 was changed as shown in Table 2. As shown in Table 3, the obtained film had excellent bending pinhole resistance, transparency, and heat-resistant dimensional stability, and also had tear straightness in the longitudinal direction of the film.

Examples 4 to 11 Instead of N 610, N69, N6 / 11, N6 / 12, N612, N
A biaxially oriented film was obtained in the same manner as in Example 1 except that 11 and N12 were used and the formulations shown in Table 2 were used. As shown in Table 3, the obtained film had excellent bending pinhole resistance, transparency, and heat-resistant dimensional stability, and had tearing straightness in the longitudinal direction of the film.

[0059]

[Table 3]

Example 12 A biaxially oriented film was obtained in the same manner as in Example 1 except that S = 0.09 m and t = 0.44 seconds, and tear straightness and bending pinhole resistance were measured. As shown in Table 4, the obtained film had excellent resistance to bending pinholes, transparency, and heat-resistant dimensional stability, and had a linear tearing property in the longitudinal direction of the film.

Example 13 A biaxially oriented film was obtained in the same manner as in Example 12 except that the stretching ratio was 5.0 times in the longitudinal direction and 3.3 times in the transverse direction, and the tear straightness and bending pinhole resistance were measured. As shown in Table 4, the obtained film had excellent bending pinhole resistance, transparency, and heat-resistant dimensional stability, and had good tear straightness in the longitudinal direction of the film.

Examples 14 to 16 Biaxially oriented films were obtained in the same manner as in Example 1 except that S, PT, D _W and t were changed as shown in Table 4, tear straightness and flex resistance. The pinhole property was measured.

The obtained film, as shown in Table 4,
It had excellent bending pinhole resistance, transparency, and heat-resistant dimensional stability, and had good tear straightness in the longitudinal direction of the film.

Example 17 Using a 200 mm φ extruder, V = 38 m / min, S, D
_A biaxially oriented film was obtained in the same manner as in Example 1 except that _W and t were changed as shown in Table 4, and the tear straightness property and bending pinhole resistance were measured. As shown in Table 4, the obtained film had excellent bending pinhole resistance, transparency, and heat-resistant dimensional stability, and had good tear straightness in the longitudinal direction of the film.

[0065]

[Table 4]

Comparative Example 1, 2 Example 1 except that the compounding ratio with N 610 was changed as shown in Table 2.
A biaxially oriented film was obtained in the same manner as. As shown in Table 5, the N6 simple substance film of Comparative Example 1 did not have straightness to tear, and the film of Comparative Example 2 had good straightness to tear, but was poor in transparency and was resistant to bending. The pinhole property was very bad.

Comparative Example 3 A biaxially oriented film was obtained in the same manner as in Example 1, except that N 66 was mixed in the weight ratio shown in Table 2 instead of N 610. As shown in Table 5, the obtained film did not have straightness to tear.

Comparative Example 4 A composition in which AN-1 was mixed in a weight ratio shown in Table 2 in place of N 610 was prepared and a biaxially oriented film was obtained in the same manner as in Example 1. As shown in Table 5, the obtained film did not have straightness to tear.

Comparative Examples 5 to 7 Biaxially oriented films were obtained in the same manner as in Example 1 except that S, PT and t were changed as shown in Table 5, tear straightness and bending pinhole resistance. Was measured. As shown in Table 5, the obtained film did not have straightness to tear.

[0070]

[Table 5]

Examples 18 to 25 and Comparative Examples 8 to 13 The multilayer film having the packaging material constitution shown in Table 6 was prepared by the dry lamination method, and the bending pinhole resistance was evaluated.

Next, using these multi-layer films, a film of the present invention is formed into a bag so that the longitudinal direction thereof is the tearing direction, whereby a four-sided sealed bag having a length of 200 mm and a width of 200 mm is formed. It was made. The abbreviations for the packaging material constructions indicate the following. ON1: Biaxially oriented film obtained in Example 1 ON6: Biaxially oriented film obtained in Example 6 ON (1): Biaxially oriented film obtained in Comparative Example 1 ON (2): Comparative Example 2 Biaxially oriented film obtained in 1. LLDPE: Linear low density polyethylene (Tokyo Cellophane Paper Co., TUX-TC, thickness 60 μm) PET: Polyethylene terephthalate film (Unitika Co., thickness 12 μm) CPP: Non-oriented polypropylene Film (Toray, thickness 60 μm) AL: Aluminum foil (Showa Aluminum, thickness 7 μm) Table 6 shows the results of evaluation of pinhole resistance and tear straightness.
Shown in

[0073]

[Table 6]

[0074]

EFFECTS OF THE INVENTION According to the present invention, a film having excellent toughness, resistance to bending pinholes, and tear straightness in the longitudinal direction of the film is provided. In addition, by using the film of the present invention in one or more layers of the film constituting the packaging bag, a packaging bag having an excellent opening property can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an IAR measuring device.

FIG. 2 is a diagram showing the shape of a test piece used for evaluation of tear straightness of a film.

FIG. 3 is a diagram showing a shape of a test piece after tearing in a tear test, (a) is an example of the test piece after tearing of a sample having good tear straightness, and (b) is poor tearing straightness. An example of the sample is shown.

[Explanation of symbols]

 1 Light source 2 Optical microscope with the lens barrel removed 3 Mirror 4 Illuminometer 5 Stage 6 Unstretched sheet 7 Notch

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location // B29K 77:00 B29L 7:00 (72) Inventor Ishikawa Atsuhiro 23 Uji Kozakura Uji-shi, Kyoto Unitika stock ceremony Central Research Institute of the Company (72) Inventor Shunichi Kawakita 31-3 Uji Hinojiri, Uji-shi, Kyoto Unitika Uji Plastic Factory

Claims (8)

[Claims] 1. A weight ratio of nylon 6 (referred to as N6) and aliphatic polyamide resin other than N6 (referred to as PA) in the range of 75 to 99.
/ 25 to 1 is a biaxially oriented polyamide film having a mixture as a main raw material, wherein the difference in surface tension (dyne / cm) between N6 and PA satisfies the formula (1) in the longitudinal direction of the film. A biaxially oriented polyamide film having linear tearability. 3.0 ≦ γ _A −γ _B ≦ 15.0 (1) where γ _A represents the surface tension of N6 and γ _B represents the surface tension of PA. 2. The weight ratio of N6 and PA is 75-99 / 25-1.
Is used as the main raw material, and the transmitted and scattered light illuminance anisotropic ratio (IA
The biaxially oriented polyamide film according to claim 1, obtained by stretching an unstretched sheet having R) of 0.1 to 0.8. 3. The biaxially oriented polyamide film according to claim 1, which has a haze of 10% or less and a shrinkage rate of 5% or less when treated at 160 ° C. for 5 minutes. 4. The PA is a polyamide resin containing 90 mol% or more of one or more of nylon 11, nylon 12, nylon 69, nylon 610 and nylon 612.
The biaxially oriented polyamide film according to any one of 1 to 3. 5. A polyamide resin, wherein PA is a polyamide resin containing 90 mol% or more of one or more of nylon 6/12 and nylon 6/11 having a copolymerization molar ratio of 10/90 to 90/10. The biaxially oriented polyamide film according to any one of claims. 6. A multilayer film having a linear tearing property, which comprises the biaxially oriented polyamide film according to claim 1 in at least one layer. 7. The multilayer film according to claim 6 is used,
An easy-open packaging bag obtained by bag making. 8. A mixture of N6 and PA in a weight ratio of 75 to 99/25 to ¹ is extruded into a sheet form from the lip gap of a die, and the shear rate of the molten polymer at that time is 100 to 400 sec ^-1.
Then, the relationship between the temperature (PT) of the molten polymer extruded from the lip gap of the die and the time (t) until the molten polymer reaches the cooling drum is controlled as follows, and the obtained unstretched sheet is obtained. Is adjusted to a moisture content of 1 to 6% by weight, and then stretched at a temperature of 150 to 220 ° C. with a stretching ratio of 2.5 times or more in each of the longitudinal and transverse directions.
Manufacturing method of axially oriented polyamide film. (1) t ≤ 1.2 when PT is in the range of 240 ≤ PT <250 ℃
Seconds. (2) t ≤ 0.9 when PT is in the range of 250 ≤ PT <260 ℃
Seconds. (3) t ≤ 0.6 when PT is in the range of 260 ≤ PT <270 ℃
Seconds. (4) t ≦ 0.3 when PT is in the range of 270 ≦ PT <280 ℃
Seconds. (5) t ≦ 0.1 when PT is in the range of 280 ≦ PT <290 ℃
Seconds.